In an existing Package-On-Package (PoP) packaging process, a bottom package is formed first, which comprises a device die bonded to a package substrate. A molding compound is then molded on the package substrate, wherein the device die is molded in the molding compound. The package substrate further comprises solder balls that are on the same side of the package substrate as the device die. The solder balls are used for connecting the bottom package to a top package. Through-molding openings are then formed in the molding compound, and hence the solder balls are exposed through the through-molding openings. In the formation of the through-molding openings, laser drill is used to remove portions of the molding compound that cover the connectors. The laser drilling is a low throughput process. Although the solder balls may be made large enough, so that the molding compound does not fully cover the solder balls, due to the large size of the solder balls, the pitch of the solder balls is also large. In addition, the stand-off height between the top package and the bottom package is also high.